Tubular knitted goods made of natural fibers together with synthetic elastomeric fibers are typically subjected to a conventional treatment process in which the knitted goods are first subjected to a relaxing process, then pre-stretched or pre-tensioned, and then heat set or fixed to have a desired width.
The conventional relaxing processes involve a heat treatment at a temperature of 100 to 110.degree. C. in order to relax the elastomeric fiber materials and ultimately achieve a uniform finished appearance and presentation of the knitted goods. Thereafter, the relaxed knitted goods are conventionally subjected to a heat setting or heat fixing of the characteristic width of the knitted goods, also known as thermosetting or thermofixing. A heat setting of the raw tubular knitted goods at a width or degree of expansion corresponding to about half of the maximum stretching range of the tubular goods is generally considered ideal. By adjusting and then fixing the width and the lengthwise extension of the raw tubular goods, suitable devices may be used to exactly prescribe and achieve the desired finished width and the desired weight per square meter of the goods.
In order to carry out the heat setting of the raw tubular goods, it has conventionally been necessary to first cut open the tubular goods along the lengthwise direction, i.e. so as to open the tubular goods into a flat single layer knitted web, which is then held under tension in a tentering frame in a flat planar condition, whereupon the heat fixing is carried out in a heat fixing apparatus. The heat fixing is carried out in the plastic deformation range of the elastomeric material of the knitted goods, namely in a temperature range of approximately 170 to 190.degree. C., with a holding or effective time of 20 to 40 seconds.
Thereafter, according to the conventional processes, the knitted web is re-formed into a tubular configuration and the cut edges are sewed to each other to again provide a tubular material, which is then subjected to further processing, such as dyeing or coloring for example. It is important to re-form the knitted goods as a tube before carrying out the further processing in order to prevent the rolling-up of the web edges, which would lead to a non-uniform coloring or dyeing of the fabric. The conventional heat fixing process involving cutting open and re-sewing the tubular goods has been found to be rather complicated and costly in practice. Moreover, this process results in substantial waste and rejection of material, due to defects arising during the cutting-open of the tubular goods before the heat setting, and the subsequent re-sewing of the goods into a tubular form.